1. Field of the Invention
The present invention relates to a ball screw device, and more particularly to a ball screw device having an inserted ball guide member for effectively and smoothly receiving and guiding the balls or the bearing members to move relative to the ball nut and the screw shaft, and thus for facilitating the rotational movement of the ball nut and the screw shaft relative to each other in great rotational speeds.
2. Description of the Prior Art
Typical ball screw devices comprise a ball nut rotatably and/or moveably engaged onto a screw shaft, and normally arranged to allow the ball nut to be rotated and/or moved relative to the screw shaft in great rotational speeds. For allowing the ball nut to be smoothly rotated and moved relative to the screw shaft, a suitable bearing device or lubricating structure is further required to be provided and engaged between the ball nut and the screw shaft, for facilitating the rotational movement between the ball nut and the screw shaft.
For example, U.S. Pat. No. 5,193,409 to Babinski discloses one of the typical ball screw devices including an inbuilt plastic insert provided or engaged into the ball nut for forming a ball return passage or an endless ball train guiding passage and for receiving a number of balls or a ball train therein, and for allowing the balls or the ball train to be engaged between the ball nut and the screw shaft to facilitate the rotational movement between the ball nut and the screw shaft.
In Babinski, the inbuilt plastic insert includes two ball return channels that are 180° reversed in orientation when in assembled position. However, due to manufacturing or machining considerations, the ball return channels of the inbuilt plastic insert should be exposed and may not be deeply formed in the inbuilt plastic insert, such that the balls or the ball train may not be effectively guided to move into the corresponding axial return passages that are formed and provided in the ball nut.
U.S. Pat. No. 5,492,036 to Sato discloses another typical ball screw device including two end caps attached to two end portions of the ball nut and having curved passages formed therein for guiding or deflecting the balls or the ball train. However, there in only one ball return passage or endless ball train guiding passage may be formed and provided between the ball nut and the ball screw and between the two end caps, such that only a limited number of the balls or the ball train may be provided and engaged between the ball nut and the ball screw.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages of the conventional ball screw devices for such as machine tools or the like.